Server-Side Copy Samba with Btrfs Enhancements

• Client offloads the copy operation to the server

• SMB2 FSCTL_SRV_COPYCHUNK supported
• Multiple chunks per request, 16M maximum offload per request
• Used by Explorer

• Samba request Btrfs clone the range of bytes

• BTRFS_IOC_CLONE_RANGE
• Meta-data operation only, no network or disk round trip
• Duplicate data does not consume disk space
• Must be Btrfs block-size aligned